Wind powered machines, particularly large scale electrical generators, include blades mounted on a hub attached to a rotor that rotates when wind passes over the blades. The rotation of the rotor is then used to drive machinery, such as pumps or electrical generators. In the case of electrical generators, the rotor will typically carry conductor windings/coils or magnetic field generators that face magnetic field generators or conductor windings/coils, respectively, on a stator such that there is relative motion between the coils and the magnetic field generators, producing electricity. The magnetic field generators are typically field windings that are electromagnets powered by the electrical generator once it begins producing electricity, but that require electricity from a battery or the like before the electrical generator produces electricity.
Large scale wind powered electrical generators are becoming more common, particularly in onshore and offshore wind farm applications. In such large scale generators, a tower supports a nacelle housing the stator, which supports the rotor, which supports the hub and blades. Equipment required for controlling the generator, including controls for the blades and other machinery, can be housed in the tower, the nacelle, and/or in cavities within the stator and/or the rotor.
An example of a large scale wind powered generator is seen in international application WO 01/29413 by Torres Martinez (equivalent to European Patent Application No. EP 1319830 A1) and entitled, “Multipolar Aerogenerator.” So-called multipolar wind power generators typically comprise a wind-driven rotor associated with a power generator housed in a nacelle atop a support tower. The nacelle is mounted for rotation on the upper end of the tower and houses electrical power generation components as well as equipment for controlling the generation of electricity, the orientation of the nacelle, the pitch of the blades, the speed of the rotor, and more. The nacelle is rotated to position the blades of the generator for maximum exposure to wind, and the pitch of the blades is similarly adjusted to optimize power generation. The rotor is secured to a rotor shaft supported by two bearings in the nacelle. The bearings are in turn supported by the housing of the nacelle, which includes the stator of the power generator. The rotor itself is comprised of a ring supported by a plurality of spokes extending radially from the shaft. The ring carries electromagnets in the form of field windings on its outer surface and facing coils mounted on the inner surface of the housing of the nacelle. Wind drives the blades, which drive the rotor shaft, which rotates the rotor and moves the electromagnetic field windings relative to the coils, generating electricity.
In such a multipolar generator, the structure of the rotor shaft and the supports in the nacelle, there is no passageway between the interior of the tower and the interior of the blades extending away from the rotor hub. Therefore, it is difficult to reach the hub for maintenance, such as to maintain blade pitch altering machinery, not to mention the rotor itself. Additionally, internal ventilation of the rotor blades, particularly for de-icing the blades, is difficult to accomplish. The construction of the wind power generator of the type disclosed by Torres Martinez is complex with regard to the support of the rotor within the stator body.
Another multipolar synchronous generator, particularly suited for horizontal axis wind power plants, is described in German patent specification DE 44 02 184 by Klinger. Klinger discloses a generator that overcomes some of the disadvantages of the type of generator disclosed by Torres Martinez by using a generator formed by one single structural unit. The single structural unit comprises a stator mounted atop a support tower, the stator being somewhat equivalent to the nacelle of Torres Martinez. The stator supports the rotor, which carries a hub to which blades are attached. As in Torres Martinez, the stator can rotate relative to the support tower to orient the blades for maximum wind exposure. The rotor is connected to the stator by a floating support provided within the generator, specifically, bearings arranged between the stator and the rotor. This single structural unit supports the rotary movement of the rotor and receives the externally introduced forces and torques. In the generator of Klinger, while the rotor shaft and related structures and components are eliminated, the structure of the rotor proves to be very complex, since the two surfaces of the rotor and of the stator lie at a considerable distance from the antifriction bearings of the rotor.